Background: Flexible flatfoot refers to downfall of the medial longitudinal arch on the weight bearing state, while it looks relatively normal in the non-weight-bearing position. The deformity has three components heel valgus, forefoot abduction and downfall of the medial longitudinal arch. Objective: This study aimed to evaluate Mosca technique in correction of all the components of the deformity of flexible flatfoot in one sitting. Patients and Methods: A prospective study on 16 feet of 16 patients (8 males and 8 females) who underwent Mosca technique for symptomatic flatfoot in the period between July 2018 and July 2020. All patients were operated upon in Zagazig University Hospitals. The mean age of the studied group was 10.4 years old, and their mean follow up period was12 months. Clinical assessment using American Orthopaedic Foot and Ankle Society (AOFAS) scoring system was performed. Radiological assessment of talonavicular coverage and talo-first metatarsal angle was done. Results: Radiological results showed median decrease in the lateral talo-metatarsal angle from 27° preoperative to 3° postoperative at last follow-up. Meanwhile the median decrease in the talonavicular angle was 33° preoperative to 6° postoperative (P < 0.05). Postoperative complications were minimal and controllable. Superficial wound infection on the lateral aspect of the foot which improved with antibiotics. Conclusions: Correction of all components of the deformity in one sitting, the technique does not use arthrodesis, so the distribution of stresses in the different foot joints is not disturbed.